1. Field of the Invention
This invention relates to a filter for removing solids or sludge from a fluid.
2. Prior Art
In U.S. Pat. No. 3,945,923, in which I am a joint inventor, a filter includes a single filter medium of fabric wound upon a tubular core, there being a screen within the filter medium and there being an additional screen between turns of the wound filter medium. In this construction, a tie string is tied tightly about the completely assembled filter module so as to insure that there will be no relaxing of the wrapped fabric material assembly. This construction is subject to a disadvantage in that a relatively thin skin of filtered-out contaminant on the filter surface causes a prohibitive pressure drop across the filter, and also determines the useful life of such filter. Attempts have been previously made with respect to other filter structures for removing such contaminant as by shaking, twisting, physical or manual cleaning, including backwashing.
If one considers a filter application wherein relatively large quantities of contaminant are to be removed, the problems described above become somewhat more aggravated.